Electronic devices containing active organic materials are attracting increasing attention for use in devices such as organic light emitting diodes (OLEDs), organic photoresponsive devices (in particular organic photovoltaic devices and organic photosensors), organic transistors and memory array devices. Devices containing active organic materials offer benefits such as low weight, low power consumption and flexibility. Moreover, use of soluble organic materials allows use of solution processing in device manufacture, for example inkjet printing or spin-coating.
An OLED may comprise a substrate carrying an anode, a cathode and one or more organic light-emitting layers between the anode and cathode.
Holes are injected into the device through the anode and electrons are injected through the cathode during operation of the device. Holes in the highest occupied molecular orbital (HOMO) and electrons in the lowest unoccupied molecular orbital (LUMO) of a light-emitting material combine to form an exciton that releases its energy as light.
Suitable light-emitting materials include small molecule, polymeric and dendrimeric materials. Suitable light-emitting polymers include poly(arylene vinylenes) such as poly(p-phenylene vinylenes) and polyarylenes such as polyfluorenes.
A light emitting layer may comprise a semiconducting host material and a light-emitting dopant wherein energy is transferred from the host material to the light-emitting dopant. For example, J. Appl. Phys. 65, 3610, 1989 discloses a host material doped with a fluorescent light-emitting dopant (that is, a light-emitting material in which light is emitted via decay of a singlet exciton).
Phosphorescent dopants are also known (that is, a light-emitting dopant in which light is emitted via decay of a triplet exciton).
A hole-transporting layer may be provided between the anode and light-emitting layer of an OLED.
WO 2009/067419 discloses compounds having formula I, formula II or formula III:

T1 and T2 are conjugated moieties which are connected in a non-planar configuration. WO 2009/084548 discloses polymers comprising a repeating unit A and a repeat unit B, wherein A is selected from divalent groups derived from compounds represented by formula (1):

wherein Ar1 to Ar4 are each independently a substituted or unsubstituted aryl group having 6 to 40 ring-forming carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 40 ring-forming atoms, or a substituted or unsubstituted alkyl group having 1 to 50 carbon atoms;
X is a substituted or unsubstituted aryl group having 6 to 40 ring-forming carbon atoms, a substituted or unsubstituted heterocyclic group having 3 to 40 ring-forming atoms, or a substituted or unsubstituted styrene-derived group; and s is an integer of 0 to 3.
EP 2233508 discloses polymers comprising a repeating unit A and a repeat unit B, wherein A includes divalent groups derived from compounds represented by formulas (1) to (4):

EP 2272894 discloses a polymer formed by polymerization of the following monomers:
